Cardiac ablation device with movable hinge

ABSTRACT

A method and apparatus for transmural ablation using an instrument containing two electrodes or cryogenic probes. A clamping force is exerted on the two electrodes or probes such that the tissue of the hollow organ is clamped therebetween. Bipolar RF energy is then applied between the two electrodes, or the probes are cryogenically cooled, thus ablating the tissue therebetween. A monitoring device measures a suitable parameter, such as impedance or temperature, and indicates when the tissue between the electrodes has been fully ablated.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/844,225, filed Apr. 27, 2001, now U.S. Pat. No. 6,517,536 which is acontinuation-in-part of U.S. application Ser. No. 09/747,609 filed Dec.22, 2000, now U.S. Pat. No. 6,546,935 and claims the benefit ofprovisional application Ser. No. 60/200,072, filed Apr. 27, 2000. Theabove applications are incorporated herein.

BACKGROUND OF THE INVENTION

Atrial fibrillation is the most common heart arrhythmia in the world,affecting over 2.5 million people in the United States alone. Ablationof cardiac tissue, in order to create scar tissue that poses aninterruption in the path of the errant electrical impulses in the hearttissue, is a commonly performed procedure to treat cardiac arrhythmias.Such ablation may range from the ablation of a small area of hearttissue to a series of ablations forming a strategic placement ofincisions in both atria to stop the conduction and formation of errantimpulses.

Ablation has been achieved or suggested using a variety of techniques,such as freezing via cryogenic probe, heating via RF energy, surgicalcutting and other techniques. As used here, “ablation” means the removalor destruction of the function of a body part, such as cardiac tissue,regardless of the apparatus or process used to carry out the ablation.Also, as used herein, “transmural” means through the wall or thickness,such as through the wall or thickness of a hollow organ or vessel.

Ablation of cardiac tissue may be carried out in an open surgicalprocedure, where the breastbone is divided and the surgeon has directaccess to the heart, or through a minimally invasive route, such asbetween the ribs or via catheter that is introduced through a vein, andinto the heart.

Prior to any ablation, the heart typically is electronically mapped tolocate the point or points of tissue which are causing the arrhythmia.With minimally invasive procedures such as via a catheter, the catheteris directed to the aberrant tissue, and an electrode or cryogenic probeis placed in contact with the endocardial tissue. RF energy is deliveredfrom the electrode to the tissue to heat and ablate the tissue (or thetissue may be frozen by the cryogenic probe), thus eliminating thesource of the arrhythmia.

Common problems encountered in this procedure are difficulty inprecisely locating the aberrant tissue, and complications related to theablation of the tissue. Locating the area of tissue causing thearrhythmia often involves several hours of electrically “mapping” theinner surface of the heart using a variety of mapping catheters, andonce the aberrant tissue is located, it is often difficult to positionthe catheter and the associated electrode or probe so that it is incontact with the desired tissue.

The application of either RF energy or ultra-low temperature freezing tothe inside of the heart chamber also carries several risks anddifficulties. It is very difficult to determine how much of the catheterelectrode or cryogenic probe surface is in contact with the tissue sincecatheter electrodes and probes are cylindrical and the heart tissuecannot be visualized clearly with existing fluoroscopic technology.Further, because of the cylindrical shape, some of the exposed electrodeor probe area will almost always be in contact with blood circulating inthe heart, giving rise to a risk of clot formation.

Clot formation is almost always associated with RF energy or cryogenicdelivery inside the heart because it is difficult to prevent the bloodfrom being exposed to the electrode or probe surface. Some of the RFcurrent flows through the blood between the electrode and the hearttissue and this blood is coagulated, or frozen when a cryogenic probe isused, possibly resulting in clot formation. When RF energy is applied,the temperature of the electrode is typically monitored so as to notexceed a preset level, but temperatures necessary to achieve tissueablation almost always result in blood coagulum forming on theelectrode.

Overheating or overcooling of tissue is also a major complication,because the temperature monitoring only gives the temperature of theelectrode or probe, which is, respectively, being cooled or warmed onthe outside by blood flow. The actual temperature of the tissue beingablated by the electrode or probe is usually considerably higher orlower than the electrode or probe temperature, and this can result inoverheating, or even charring, of the tissue in the case of an RFelectrode, or freezing of too much tissue by a cryogenic probe.Overheated or charred tissue can act as a locus for thrombus and clotformation, and over freezing can destroy more tissue than necessary.

It is also very difficult to achieve ablation of tissue deep within theheart wall. A recent study reported that to achieve a depth of ablationof 5 mm, it was necessary to ablate an area almost 8 mm wide in theendocardium. See, “Mechanism, Localization, and Cure of AtrialArrhythmias Occurring After a New Intraoperative EndocardialRadiofrequency Ablation Procedure for Atrial Fibrillation,” Thomas, etal., J. Am. Coll. Cardiology, Vol. 35, No. 2, 2000. As the depth ofpenetration increases, the time, power, and temperature requirementsincrease, thus increasing the risk of thrombus formation.

In certain applications, it is desired to obtain a continuous line ofablated tissue in the endocardium. Using a discrete or point electrodeor probe, the catheter must be “dragged” from point to point to create aline, and frequently the line is not continuous. Multielectrodecatheters have been developed which can be left in place, but continuitycan still be difficult to achieve, and the lesions created can be quitewide.

Because of the risks of char and thrombus formation, RF energy, or anyform of endocardial ablation, is rarely used on the left side of theheart, where a clot could cause a serious problem (e.g., stroke).Because of the physiology of the heart, it is also difficult to accesscertain areas of the left atrium via an endocardial, catheter-basedapproach.

Recently, epicardial ablation devices have been developed which apply RFenergy to the outer wall of the heart to ablate tissue. These devices donot have the same risks concerning thrombus formation. However, it isstill difficult to create long, continuous lesions, and it is difficultto achieve good depth of penetration without creating a large area ofablated tissue.

As noted above, other forms of energy have been used in ablationprocedures, including ultrasound, cryogenic ablation, and microwavetechnology. When used from an endocardial approach, the limitations ofall energy-based ablation technologies to date are the difficulty inachieving continuous transmural lesions, and minimizing unnecessarydamage to endocardial tissue. Ultrasonic and RF energy endocardialballoon technology has been developed to create circumferential lesionsaround the individual pulmonary veins. See e.g., U.S. Pat. No. 6,024,740to Lesh et al. and U.S. Pat. Nos. 5,938,660 and 5,814,028 to Swartz etal. However, this technology creates rather wide (greater than 5 mm)lesions which could lead to stenosis (narrowing) of the pulmonary veins.See, “Pulmonary Vein Stenosis after Catheter Ablation of AtrialFibrillation,” Robbins, et al., Circulation, Vol. 98, pages 1769-1775,1998. The large lesion area can also act as a locus point for thrombusformation. Additionally, there is no feedback to determine when fulltransmural ablation has been achieved. Cryogenic ablation has beenattempted both endocardially and epicardially (see e.g., U.S. Pat. Nos.5,733,280 to Avitall, 5,147,355 to Friedman et al., and 5,423,807 toMilder, and WO 98/17187, the latter disclosing an angled cryogenicprobe, one arm of which is inserted into the interior of the heartthrough an opening in the heart wall that is hemostatically sealedaround the arm by means of a suture or staples), but because of the timerequired to freeze tissue, and the delivery systems used, it isdifficult to create a continuous line, and uniform transmurality isdifficult to verify.

Published PCT applications WO 99/56644 and WO 99/56648 disclose anendocardial ablation catheter with a reference plate located on theepicardium to act as an indifferent electrode or backplate that ismaintained at the reference level of the generator. Current flows eitherbetween the electrodes located on the catheter, or between theelectrodes and the reference plate. It is important to note that thisreference plate is essentially a monopolar reference pad. Consequently,there is no energy delivered at the backplate/tissue interface intendedto ablate tissue. Instead, the energy is delivered at theelectrode/tissue interface within the endocardium, and travels throughthe heart tissue either to another endocardial electrode, or to thebackplate. Tissue ablation proceeds from the electrodes in contact withthe endocardium outward to the epicardium. Other references discloseepicardial multielectrode devices that deliver either monopolar orbipolar energy to the outside surface of the heart.

It is important to note that all endocardial ablation devices thatattempt to ablate tissue through the full thickness of the cardiac wallhave a risk associated with damaging structures within or on the outersurface of the cardiac wall. As an example, if a catheter is deliveringenergy from the inside of the atrium to the outside, and a coronaryartery, the esophagus, or other critical structure is in contact withthe atrial wall, the structure can be damaged by the transfer of energyfrom within the heart to the structure. The coronary arteries,esophagus, aorta, pulmonary veins, and pulmonary artery are allstructures that are in contact with the outer wall of the atrium, andcould be damaged by energy transmitted through the atrial wall.

Accordingly, it is the object of the present invention to provide animproved method and device for making transmural ablations to hearttissue.

It is a related object to provide a method and device for makingtransmural ablation in heart tissue that minimizes unnecessary damage tothe heart tissue.

It is a related object to provide a method and device for makingtransmural ablation in heart tissue that minimizes unnecessary damage tothe heart tissue.

It is a further object to provide a method and device for makingtransmural ablation in heart tissue that creates continuous lesions in asingle step.

It is still a further object to provide a method and device formonitoring the electrical conductivity of the tissue in the transmurallesion simultaneously with the creation of the lesion.

It is also an object to provide a method and device for measuring thetemperature of the tissue forming the lesion simultaneously with itscreation.

SUMMARY OF THE INVENTION

These objects, and others which will become apparent upon reference tothe following detailed description and attached drawings, are achievedby the use of a clamping and ablating device for use in treating cardiacarrhythmia having first and second handle members, with first and secondmating jaw members associated with the first and second handle members,respectively. The jaw members are movable by the handle members betweena first open position and a second clamped position, and the jaw membershave insulated outer surfaces which may have convex, opposed matingsurfaces. Each mating surface has a central region, with the centralregion of the first jaw being aligned with the central region of thesecond jaw. A first elongated electrode extends along the central regionof the first jaw and a second elongated electrode extends along thecentral region of the second jaw. The first and second electrodes areadapted to be connected to an RF energy source so that, when activated,the electrodes are of opposite polarity. In a preferred embodiment, theelectrodes are made of gold-plated copper and measure betweenapproximately 3 to 8 cm in length and approximately 0.12 to 0.6 mm inwidth. By the use of such a device a clamping zone is created that iswider than the contact zone of the electrodes with the tissue. Thispermits the ablation to be performed with a minimum of contact betweenthe electrodes and any blood cells, thus greatly reducing the likelihoodof thrombus. The design also allows for a minimum distance between theelectrodes, further encouraging complete, transmural ablation thatcreates a continuous lesion in a single step.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a procedure in accordance with thepresent invention utilizing ablation elements operatively connected toeither a source of RF energy or cryogenic fluid.

FIG. 2 is a cross-section of an ablation element for use in the presentinvention taken along lines 2-2 of FIG. 1.

FIGS. 3-6 show alternate configurations for the ablation elements ofFIG. 2.

FIG. 7 shows a further step in the inventive procedure in which tissueis clamped between the ablation elements.

FIGS. 8-12 schematically illustrate the inventive procedure so as tomake a transmural lesion that fully circumscribes a pulmonary vein, withFIG. 9 showing a cross-sectional view of the clamp/ablation element incontact with the atrial tissue to express blood from the clamped area.

FIGS. 13-17 show a further method according to the present invention inwhich transmural lesions are made so as to circumscribe both pulmonaryveins.

FIGS. 18-22 show a further procedure in which a transmural lesion ismade so as to circumscribe a single pulmonary vein.

FIGS. 23-27 illustrate a further procedure in which a transmural lesionis made so as to circumscribe both pulmonary veins.

FIG. 28 is a perspective view of a further embodiment of a grasper foruse in an open chest procedure in accordance with the present inventionshowing the grasper in its “closed” position.

FIG. 29 is a perspective view of the grasper of FIG. 28 with the grasperin its “open” position.

FIG. 30 is an enlarged perspective view of the working position of thegrasper of FIG. 28 with the grasper jaws in the “closed” position.

FIG. 31 is an enlarged perspective view of the working portion of thegrasper of FIG. 28 with the grasper jaws in the “open” position.

FIG. 32 is an enlarged cross-sectional view of the grasper jaws for thegrasper of FIG. 28.

FIG. 33 is a perspective view of a further embodiment of a grasper,which may be used in either an open or a minimally invasive procedure,along with its associated electrosurgical generator.

FIG. 34 is a side view of the grasper of FIG. 33 showing the grasper inits “open” position.

FIG. 35 is an exploded perspective view of the grasper of FIG. 33.

FIG. 36 is a side cross-sectional view of the grasper of FIG. 33 withthe grasper jaws in the “open” position.

FIG. 37 is a side cross-sectional view of the grasper of FIG. 33 withthe grasper jaws in the “closed” position.

FIG. 38 is a cross-sectional view taken along line 38-38 of FIG. 34showing the grasper jaws in the “open” position.

FIG. 39 is a cross-sectional view of the grasper jaws taken along theline 39-39 of FIG. 37 showing the grasper jaws in the “closed” position.

FIG. 40 is a cross-sectional view of the graspers taken along line 40-40of FIG. 34.

FIGS. 41-51 show alternate constructions for the electrodes suitable foruse in the present invention, with FIGS. 41 and 43-51 beingcross-sectional views similar to FIGS. 38 and 39, and FIG. 42 being across-sectional view taken along line 42-42 of FIG. 41.

FIGS. 52A-K illustrate eleven different ablations to the left and rightatrium (as seen from behind in FIG. 52A) and the methods for making thelesions (FIGS. 52B-K).

FIG. 53A is a perspective view of a further embodiment of device forperforming transmural ablation according to the present invention.

FIG. 53B is a perspective view of the transmural ablation device of FIG.53A with a portion removed to show detail.

FIG. 54 is an exploded perspective view of the transmural ablationdevice of FIG. 52.

FIG. 55 is a longitudinal cross-sectional view of an obturator tipelectrode for use in the device of FIG. 52.

FIG. 56 is a piercing tip electrode for use in the device of FIG. 52.

FIG. 57 is an enlarged side view of the tip of the instrument shown inFIG. 52.

FIGS. 58A-58G illustrate the use of the instrument of FIG. 52 to form atransmural ablation.

FIG. 59 shows a series of transmural ablations contemplated by the MAZEprocedure.

FIGS. 60A-60I illustrate a procedure for performing a circumferentiallesion in lumen such as a pulmonary vein.

FIG. 61A-61J show the use of the instrument of FIG. 52 for forming acontinuous transmural ablation around a pair of pulmonary veins.

FIG. 62A-I show a further device for performing transmural ablations andthe method for making such ablations.

FIG. 63 is a perspective view of a further embodiment of a grasperadapted for use in minimally invasive procedures.

FIG. 64 is an enlarged plan view of the handle position of the grasperof FIG. 63, with portions removed to show detail.

FIGS. 65A and 65B are enlarged plan views of the jaw actuation mechanismfor the grasper of FIG. 63.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to the present invention, the compression of the atrialtissue is important because it insures that the exposed electrodesurface or cryogenic probe is not in contact with any tissue or bloodexcept the clamped tissue to be ablated. Specifically, the clamping ofthe tissue between the electrodes or cryogenic probes insures that theconductive or cooled area is only in contact with the clamped tissue.The compressed tissue acts to isolate the electrically active orcryogenically cooled surface, and prevents inadvertent energy deliveryto other parts of the heart or blood. The outside temperature of theelectrode can easily be monitored to insure that the temperature of theinsulation in contact with blood remains below a critical temperature(40° C., for example).

In one form of the invention, transmural ablation using RF energy isaccomplished by providing an atrial ablation device having a lower “j”clamp/electrode element and placing it on the atrial tissue below thepulmonary veins.

Once the pulmonary veins have been isolated, an upper clamp/electrodeelement is introduced, and the clamp assembly “J” is worked back ontothe epicardial atrial tissue. Once the jaws are positioned below theostia of the pulmonary veins, the tissue is partially clamped, allowingcontinued flow from the pulmonary veins to the left atrium. Once theclamps are safely away from the pulmonary vein tissue, and onto atrialtissue, the clamps are closed together to compress the tissue. Once thetissue is compressed, bipolar RF energy is used to ablate the clampedatrial tissue. The clamps are then removed, the lesion having beencreated. Lesions may also be created by inserting one clamp/electrodeelement through an incision in the heart so as to permit contact withendocardial tissue. This incision may be created with a separateinstrument. Alternatively, the tip of one of the jaws may have apiercing structure associated therewith for making the entry incision.Once the clamps are properly located, the tissue is compressed and RFenergy is applied.

Turning now to the figures of the drawings, a method embodying thepresent invention is shown schematically in FIG. 1. A clamping typedevice 10 is provided to group the two walls 22, 24 of the atrium 20,and delivers bipolar RF energy through both walls held between the twoupper and lower clamp jaws 50, 51. FIG. 1 shows the upper and lowerclamp jaws 50, 51 and electrodes 52, 53 positioned above and belowatrial tissue 22, 24, distal to the pulmonary veins. FIG. 2, Section 2-2of FIG. 1, shows a cross-section of the clamping member including theinsulator 28 and electrode 53. Alternate configurations of the clampingmembers are shown in FIGS. 3-6. FIG. 3 shows a cross section of theelectrode consisting of an insulating layer 11, and a conductive strip12. The electrode of FIG. 3 may be constructed of a tungsten wire as theconductive material 12, with polyamide as the insulating material 11.The conductive strip is created by exposing a part of the tungsten wirethrough the polyamide. FIGS. 4 and 5 show an alternate electrodeconstruction consisting of a carbon fiber element 13, and an insulatingmaterial 14, such as ABS. The conductive strip 15 may be comprised of acopper/gold electrode plated onto the ABS. FIG. 6 shows a cross sectionof yet another possible electrode design where the conductive material16 consists of a stainless steel needle with lumen 17 and insulatingmaterial 18.

FIG. 7 shows the jaws 50, 51 clamping and ablating the atrial tissue 20distal to the pulmonary veins 26. Proximal point A is clamping andablating the atrial tissue distal to the pulmonary veins. Proximal pointA is the most proximal point of ablated tissue on both the upper andlower atrial wall. Distal point B is the most distal point of ablatedtissue on both the upper and lower atrial wall.

FIGS. 8-12 show the inventive procedure that fully circumscribe apulmonary vein with transmural lesions. FIG. 8 shows a top view of theinstrument jaws positioned for a 2-step isolation of a single pulmonaryvein. The lower jaw is directly beneath the upper jaw, and is not shown.Proximal point A and distal point B correspond to FIG. 7.

FIG. 9 shows a cross-sectional view of the jaws clamping and ablatingatrial tissue. Importantly, FIG. 9 shows that the electrode/clampconfiguration provides a clamped zone of tissue that is wider than thezone of ablated tissue. This is achieved by using an electrode widththat is narrower than the clamped tissue width. As shown in FIG. 9 (andbetter illustrated in FIG. 26), the electrode forms the apex of thetriangular clamping member. Other convex shapes are also contemplated.

The wider zone of clamped tissue serves several purposes. When theclamping members are closed onto tissue, any blood in the clamped zoneis squeezed or expressed out. Further, the distance between theelectrodes is minimized, so that the ablation zone remains narrow. It isimportant to isolate the blood from the ablation zone to avoid creatingthrombus. Accordingly, a clamped zone that isolates the ablation zonefrom the blood minimizes the temperature at the periphery of theablation zone and will reduce the likelihood of the formation ofthrombus by the blood in contact with the clamped zone.

Once tissue has been fully ablated with the clamp in the position shownin FIG. 8, an ablation line of tissue on both upper and lower atrialwalls is created. This is shown as ablation line 60 in FIG. 10. Theclamp is then repositioned to the position shown in FIG. 10, so that thedistal point D overlaps the ablation line 60. The tissue is clamped andablated as shown in FIGS. 7 and 9, and a second ablation line 61 (FIG.11) is formed on both the upper and lower atrial walls. Proximal point Cand distal point D correspond to points A and B respectively. The fullablation line is shown in FIGS. 11 and 12 with points A-D as shown.

This “clamping” method and device for creating transmural lesions has anumber of advantages. First, using a two step method as shown allows forclamping and ablation of atrial tissue without stopping the blood flowfrom the pulmonary vein. Secondly, by clamping both walls together, anddelivering energy through the clamped tissue, the atrial tissue is notpenetrated. Because the atrial tissue is not penetrated, a larger jawcan be used, and the clamping force can be much higher because of theincreased stiffness of the jaw. Also, there is no concern of bleedingfrom an atrial puncture.

Another advantage of this method and device is that ablation of tissuewithin the pulmonary veins is avoided, as recent articles have shownthat ablation of tissue within the pulmonary veins can cause pulmonaryhypertension and stenosis. Specifically referring to FIGS. 13-17, alonger jaw could be used to create an ablation line through atrialtissue which electrically isolates both pulmonary veins using the samemethod.

FIGS. 18-22 show the clamping device in a curved embodiment that createsa circumferential lesion around the pulmonary vein in one step. FIGS. 18and 19 show the clamp jaws positioned around the pulmonary vein. FIGS.20 and 21 show the device clamping and ablating atrial tissue distal tothe pulmonary vein. FIG. 22 shows the resulting ablation line 60.

FIGS. 23-27 show the same concept applied to a device and method forcreating a lesion around both pulmonary veins. The advantage of thisconcept is that the entire lesion is created in one step. Thedisadvantage is that blood flow from the pulmonary vein(s) is cut offduring ablation. Using a curved electrode also allows the user to ablatetissue more distal to the pulmonary vein than would be possible with astraight electrode. Note that this curved type electrode could be usedwith a two step procedure as described above, using “left” and “right”curved devices to create a lesion which was more distal to the pulmonaryveins. Note also that this method and device are not limited to usearound the pulmonary veins, but could be used anywhere in the atriumthat the clamp could be applied.

Turning to FIGS. 28-32, there is seen a further version of a cardiacgrasper 70 suitable for an open chest procedure in accordance with thepresent invention. The grasper 70 includes two ring handles 72, 74joined together for relative movement by a pivot screw or pin 76. Eachhandle 72, 74 has a jaw member 78, 80 respectively associated therewith,each jaw being curved so that it has a major portion that issubstantially perpendicular to the handles. This gives the grasper 70 anL-shaped appearance, with a working portion of the jaws being betweenapproximately 3-8 cm in length.

The grasper is made of a rigid material, such as stainless steel, and issubstantially encased in a durable insulating material, such as ABSplastic. With reference to FIG. 32, which shows the opposed jaw membersin cross section, the stainless steel structural support is designated82. The structural support 82 is completely encased by insulatingmembers 84, 86 and 88. The tips 78 a, 80 a of the jaws may be made of asoft, atraumatic material in order to reduce the likelihood ofunintentional injury of tissue by the jaws.

In keeping with the invention, the grasper jaws have raised or convex,opposed tissue clamping surfaces, 90, 92, respectively, with eachclamping surface, 90, 92 centrally supporting an electrode 94, 96,respectively, of opposite polarity. RF energy of opposite polarity issupplied to the electrodes 94, 96 through conductors 98, 100, which areconnected to an RF generator. As with the previously-described jawmembers, this electrode/clamp configuration provides a clamped zone oftissue that is significantly wider than the zone of ablated tissuecreated by the opposed electrodes. This causes for any blood in theclamp zone to be squeezed or expressed out of the ablation zone, thusreducing the likelihood of thrombus formation, as well as minimizing thedistance between the electrodes, so that the ablation zone remainsnarrow. The clamping also eliminates the cooling effect of circulatingblood.

With reference to FIG. 32, the electrodes 94, 96 have a T-shaped crosssection, with the cross portion of the T resting on the insulatingmember 88 and the upright portion of the T protruding through a narrowopening in the insulating member 84, thus creating an exposed electrodesurface that contacts the tissue grasped between the jaws. In practice,the electrodes are preferably made of gold-plated copper and extendalong substantially the entire working surface of the jaw members. Theexposed portions of the electrode are generally between approximately0.12-0.6 mm in width.

In keeping with a further aspect of the invention, the graspers mayprovide feedback that permits the user to gauge the completeness (i.e.,degree of transmurality) of the ablation. Specifically, a transmurallesion blocks electrical signals because it is non-conductive scartissue. Because impedance is simply the inverse of conductivity, theability of the lesion to block electrical signals is accuratelyindicated by its impedance, which can be measured simultaneously withthe creation of the lesion. During RF energy application to the tissueto be ablated, the current and voltage applied to the tissue aremeasured, and the impedance calculated and stored. Based upon a functionof the impedance (e.g., its value, the change in value, or the rate ofchange in value)) it is determined whether ablation is complete andtransmural. See e.g., U.S. Pat. No. 5,403,312, which is incorporated byreference herein. Indicator lights or other types of signals (e.g.,audible may be associated with the grasper to correspond to the degreeof ablation determined by the impedance feedback system. For example,once the impedance reaches a certain level for a certain period of time,a red light may be activated to signal that ablation is complete.

In keeping with another aspect of the invention, a feedback system fordetermining the temperature of the ablated tissue is also provided. Tothis end, the jaws include a series of thermocouples 102 that aresupported in the insulating member 84 and protrude slightly therethroughso as to engage any tissue clamped between the jaws 72, 74. Wires 104are attached to the thermocouples 102 to transmit the informationreceived to a remote location. Again, a visual or other indicator may beprovided to alert the user that a certain pre-determined criticaltemperature (e.g., 40° C.) has been reached.)

Turning to FIGS. 33-37, there is a further version of a cardiac grasper110 suitable for both open and minimally-invasive procedures inaccordance with the present invention. As seen in FIG. 33, the grasper110 includes a cord 112 for housing the conductors (not shown) and forplugging into an electrosurgical generator 114 to provide current to thegrasper 110. As discussed above, the generator 114 includes a display115 to provide a simultaneous visual indication of the degree ofconductance of the tissue being ablated. The instrument 110 includesopposed jaw assemblies 116, 118 with jaw assembly 116 being fixed andjaw assembly 118 being movable between an open position (as seen inFIGS. 34 and 36) to a closed position (shown in FIG. 37). The fixed jawassembly 116 comprises a fixed electrode 120, a fixed insulator 122 anda fixed jaw cap 124. The fixed electrode 120 provides an electricalpathway adjacent to the tissue to be ablated and is located on theinside of the fixed jaw assembly 116 (the “inside” being defined as theside that contacts the tissue to be ablated). The fixed insulator 122surrounds the fixed electrode 120 and forms the inside of the fixed jawassembly 116. The fixed jaw cap 124 forms the backside of the fixed jawassembly 116 (the “backside” being defined as the surface opposite thefixed electrode 120).

The drive jaw assembly 118 comprises a drive electrode 126, a driveinsulator 128, and a drive jaw cap 130. The drive electrode 126 providesa second electrical pathway adjacent the tissue to be ablated and islocated on the inside of the drive jaw assembly 118 (“inside” beingdefined as the side contacting the tissue to be ablated). The driveinsulator 128 surrounds the drive electrode 126 and forms the inside ofthe drive jaw assembly 118. The drive jaw cap 130 forms the backside ofthe drive jaw assembly 118 (“backside” being defined as the surfaceopposite the drive electrode 126).

Each of the electrodes 120, 126 is attached to an electricallyconductive means, such as a wire, that runs the length of the extensionshaft and through the conductor cord 112 for coupling to the RFgenerator 114.

Each jaw assembly 116, 118 is supported by a two piece extension shaftcomprising a right fixed member 132 and left fixed member 134 (for thefixed jaw) and a right drive member 136 and left drive member 138 (forthe drive jaw 118). A shaft cap 139 covers the coextensive portions ofthe fixed members 132, 134 and the drive members 136, 138 (when the jawsare in the open position as seen in FIG. 34). The right fixed member 132and left fixed member 134 combine to form a structure that extends froma handle 140, through the shaft cap 139, and then terminating at thedistal end of the instrument 110 in the fixed jaw assembly 116 on theright and left sides, respectively, of the instrument. Similarly, theright drive member 136 and left drive member 138 extend from the handle140, through the shaft cap 139, and then terminate in the drive jawassembly 118 on the right and left sides, respectively, of theinstrument. The portions of the fixed members 132, 134 co-extensive withthe fixed jaw assembly 116 are joined by a fixed bridge 142 along thelength of the jaw. Similarly, the portions of the drive members 136, 138co-extensive with the drive jaw assembly 118 are joined together by adrive bridge 144 along the length the drive jaw 118.

The handle 140 comprises two mating halves 140 a, 140 b forencapsulating the actuation and force control mechanisms for thegrasper, as well as providing for grounding of the shaft components bymeans of a conductive shaft pin 141. In order to move the drive jawassembly 118 between its open and closed positions, the handle 140includes a lever comprising a pair of lever plates 146 and a levershroud 148. The lever is pivotally mounted on a support member 150extending between the two halves 140 a, 140 b of the handle 140, with alever spring 151 biasing the lever to its open position (FIG. 34). Thelever plates 146 are coupled by a lever pin 152 to a carriage 154 thatcaptures the proximal ends of the drive members 136, 138, so as toprovide translational motion to these members.

The carriage 154 includes a lost motion assembly comprising a carriagespring 156 for controlling the minimum and maximum loads that can beapplied to tissues that are to be captured between the jaw assemblies116, 118. (The range of tissue thickness is expected to be between about1-15 mm.) This is accomplished by pre-loading the carriage spring 156with a load adjustment screw 158. The lost motion assembly also includesa thumb latch 160 for releasing the clamping pressure and for providinga mechanical stop for the spring-loaded carriage 154. The thumb latch160 is pivotally mounted on a latch pin 162 to secure the thumb latch tothe handle 140. Additionally, a latch spring 164 is provided for biasingthe thumb latch 160 to its locked position. A latching step on thecarriage 154 interfaces with the tip of the thumb latch 160 to providefor the mechanical stop.

When the lever is pivoted with respect to the handle 140, the drive jawassembly 118 and its drive members 136, 138 slide along the longitudinaldirection of the shaft to bring the two jaw assemblies 116, 118 intocontact with the tissue intended to be grasped.

In order to ablate a narrow, long region of biological tissue with theinstrument 110, the tissue is first placed between the open instrumentjaws 116, 118. The user then grasps the actuation lever comprising thelever plates 146 and lever shroud 148 to apply the force required todrive the drive members 136, 138 and drive jaw assembly 118 distally,thus compressing the tissue. and automatically engaging the thumb latch160. The thumb latch 160 locks the position of the drive members 136,138 and the drive jaw assembly 118 with respect to the handle 140 andthe fixed jaw assembly 116. The amount of jaw force on the tissue iscontrolled by the lost motion assembly between the lever and the drivemembers 136, 138.

With the jaws closed on the tissue, the operator activates the RFgenerator 114. RF energy passes through the tissue between theelectrodes 120, 126, thus ablating the tissue between these electrodes.After completion of the ablation cycle, the operator releases theclamping of the tissue by depressing the thumb latch 160, thus releasingthe carriage 154. With the carriage 154 released, the lever spring 151drives the drive members 136, 138 and the drive jaw assembly 118proximally to their open positions. The actuation lever, since it isdirectly coupled to the carriage 154, also returns to the open position.

Turning to FIGS. 41-51 there is seen in schematic form variousconfigurations for the electrodes 120, 126 for use in conjunction withthe grasper 110. Each of FIGS. 41 and 43-51 show a cross-section throughthe instrument jaws as clamped on the tissue to be ablated. Eachelectrode is formed of a piece of electrically conductive metal that maybe plated with a biocompatible material.

With reference to FIGS. 41 and 42, the electrode geometry consists of alargely rectangular electrode with a window of material removed from thecentral region. The window area is filled with the insulator material122, 128. At the clamping surface the electrode insulator material leadsaway from the electrode on a radius. The electrode material protrudesoutside the clamping surface of the insulating material. However, theelectrode may also be flush with the clamping surface.

With reference to FIG. 43, the electrode geometry is largely rectangularand the electrode insulator material leads away from the electrode on aradius. The electrode is flush with the clamping surface of theinsulator material.

With reference to FIG. 44, the electrode is applied to fill a grove inthe insulator material by way of a plating process. The electrodegeometry is largely rectangular and the electrode insulator materialleads away from the electrode on a radius. The electrode plating islargely flush with the clamping surface of the insulator material.

With reference to FIG. 45, the electrode is formed into a U-shapedelement. The electrode insulator material leads away from the electrodeon a radius. As shown, the electrode material extends outside theclamping surface of the insulator material. However, the electrodematerial may also be flush with the insulator clamping surface.

With reference to FIG. 46, the electrode is applied to fill a grove inthe insulator material by way of a plating process, with the electrodegeometry being largely rectangular. The electrode insulator materialcreates a small flat surface perpendicular to the closure plane that islargely flush with the surface of the plate or electrode. As shown, theelectrode material is flush with the clamping surface of the insulatormaterial. However, the electrode material may also be applied so that itextends outside the insulator clamping surface.

With reference to FIG. 47, the electrode geometry is largely rectangularand the electrode insulator material leads away from the electrode on aradius. The electrode material extends outside the clamping surface ofthe insulator material.

With reference to FIG. 48, the electrode configuration is again largelyrectangular, with the electrode insulator material creating a small flatsurface perpendicular to the closure plane that is largely flush withthe surface of the plate or electrode. The electrode is flush with theclamping surface of the insulator material and a temperature sensingmeans, such as a thermocouple 166 (see also FIGS. 36 and 39), ispositioned in close proximity to the electrode, but electricallyisolated from the RF energy.

With reference to FIG. 49, the electrode is applied to fill a grove inthe insulator material by way of a plating process. The electrodegeometry is largely rectangular and the electrode insulator materialleads away from the electrode on a radius.

With reference to FIG. 50, the electrode is applied to the surface ofthe electrode insulator material by way of a plating process. Theelectrode geometry is largely rectangular with the electrode insulatormaterial leading away from the electrode on a radius. The electrodeplating is largely flush with the clamping surface of the insulatormaterial. With reference to FIG. 51, the electrode is round wire madefrom an electrically conductive metal that may be plated with abiocompatible material. The electrode insulator material leads away fromthe electrode on a radius. As shown, the electrode material extendsoutside the clamping surface of the insulator material. However, theelectrode material may also be flush with the insulator clampingsurface.

A further embodiment of a grasper according to the present invention isshown in FIGS. 63-65 and is designated generally 250. The grasper 250has jaws 252, 254 similar in structure to those described above inconnection with the embodiments of FIGS. 28-32 and 33-40, but includes adifferent actuation mechanism. Specifically, the jaws 252, 254 of thegrasper 250 are biased so that they are normally in the closed position,the jaws being moved to the open position by moving the two handlemembers 256, 258 towards each other. This action serves to withdraw apush-rod 260 (FIG. 64), which is pivotally connected to the handlemembers 256, 258 by links 262, 264. With reference to FIG. 65A and FIG.65B. The distal end of the push rod 260 includes two pins 266, 268 whichare captured in slots 270, 272 in their respective jaw members 252, 254.When the pins 266, 268 are located in the distal ends of the slots 270,272, the jaws are in the closed position. The jaws 252, 254 open as thepins 266, 268 move proximally in the slots 270, 272 through thewithdrawal of the push rod 260 by the closing of the handle members 256,258.

The jaws 252, 254 also include a lost motion connection including aspring to bias the jaws toward the closed position. With reference againto FIG. 65A and FIG. 65B, the jaws 252 and 254 are pivotally connectedto each other by means of a pin 274. The pin 274 is secured to the jawmember 254, but is received in an elongated slot 276 in jaw member 252.The pin 274 is biased to the top of the slot 276, thus biasing the jaws252, 254 to the closed position, by means of a leaf spring 278 havingone end secured to the pin 274 and the other end captured between twostuds 280, 282 carried on the jaw member 252.

FIGS. 52A-K illustrate a series of 11 different lesions or ablationsthat may be made using either an open or a minimally invasive techniquewith the graspers described above. Turning first to FIG. 52A, there isseen a view of the heart showing the right and left atriums (as viewedfrom behind). The heart includes the left atrial appendage (LAA) and theright atrial appendage (RAA). The right pulmonary veins (RPVs) and leftpulmonary veins (LPVS) enter into the top of the left atrium. Thesuperior vena cava (SVC) and inferior vena cava (IVC) are also shown.The mitral valve annulus is designated as MVA, while the tricuspid valveannulus designated TVA. In FIG. 52A, 11 different lesions are indicatedby the reference numerals 1-11. A method for making each of theselesions is illustrated in the following FIGS. 52B-K. It should beappreciated that, depending upon a particular patient's indications, thelesions 1-11 may be created in a variety of combinations.

With reference to FIG. 52B, a method for making lesion 1 to circumscribethe right pulmonary veins (RPVs) is shown. This lesion is madecompletely epicardially in a manner similar to that illustrated in FIGS.23-27. FIG. 52C illustrates lesion 2, an epicardial ablation that fullycircumscribes the left pulmonary veins (LPVs). Again, this lesion may bemade in a manner similar to that illustrated in FIGS. 23-27.

FIG. 52D illustrates a method for making lesion 3, which connectslesions 1 and 2. Lesion 3 is made with only one of the jaws of thegraspers being located epicardially. The mating jaw is inserted into theinterior of the heart through a small incision which is sealed using apurse-string suture. The incision as illustrated is made interior thelesion 1 encircling the right pulmonary veins (RPVs).

Lesion 4 connects the lesion 1, which surrounds the right pulmonaryveins, to the mitral valve annulus (MVA). It may be made through thesame incision and purse-string suture used for making lesion 3. Withreference again to FIG. 52D, the jaws of the grasper are merely rotateddown so that the distal end of the jaw overlies the mitral valveannulus.

It may also be desirable to make a lesion between the superior vena cava(SVC) and the inferior (IVC). This may be created in two steps, in whichlesions 5 and 6 are made. With reference to FIG. 52E, an incision withpurse-string suture is made approximately midway between the SVC andIVC, with one of the jaws of the grasper being inserted into theincision so as to have its end adjacent the base of the SVC. The lesion5 is formed and then the instrument is rotated 180° as shown in FIG.52F, to make lesion 6. Lesion 7 may conveniently be made through thesame incision and purse-string suture as lesions 5 and 6, as shown inFIG. 52G. Lesion 7 extends from between the SVC and IVC out toward theright atrial appendage (RAA).

A lesion 8 is made between the right atrial appendage and the tricuspidvalve annulus (TVA) utilizing an incision and purse-string suture madein the RAA, as illustrated in FIG. 52H. Lesion 8 is made on the oppositeside of the right atrium as lesion 7, and thus is shown in dotted linein FIG. 52A. A lesion 9 may also be made circumscribing the right atrialappendage so as to intersect both lesions 7 and 8. As shown in FIG. 52I,lesion 9 is made epicardially. A similar epicardial ablationcircumscribing the left atrial appendage is designated 10 andillustrated in FIG. 52J.

A final lesion 11 is illustrated that connects lesion 10 circumscribingthe left atrial appendage with lesion 2 that circumscribes the leftpulmonary veins. As illustrated, the lesion 11 is made utilizing anincision and purse string suture through which the grasper jaw isintroduced, the incision being located in the left atrial appendagebeyond the lesion 10.

In a further embodiment, the present device consists of two long,linear, wire-type electrodes, which are in parallel relationship to eachother, each approximately 1 mm in diameter, and 50 mm long. Theelectrodes are insulated along their entire surface with a thin layer ofhigh dielectric material such as polyamide, except for a thin strip ofelectrically conductive material that runs along the length of eachelectrode, in face-to-face relationship with each other. The electrodesare comprised of a high modulus material, such as tungsten or carbonfiber.

One of the electrodes is designed to be introduced into the interior ofa hollow organ through a small puncture wound in the wall of the organ.The second electrode is introduced on the opposite side of the holloworgan wall. The device incorporates a mechanism for advancing eachelectrode individually, or both simultaneously, in parallel relationwith each other. The device also includes a clamping mechanism thatbrings the two electrodes together so that their exposed conductivesurfaces are in face-to-face relation and the electrodes exertsufficient pressure to clamp the tissue. Once both electrodes have beenadvanced to their desired positions, the clamping mechanism is activatedwhich brings the two wires together, and clamps the tissue between thetwo exposed electrode surfaces. RF energy is then applied between thetwo electrodes, and the tissue is ablated in a long, continuous,transmural line. A monitoring device measures the voltage, current,impedance, and/or temperature between the two electrodes, and analgorithm determines whether the tissue is fully ablated.

This device provides a way to achieve and verify a fully transmural andcontinuous line of tissue ablation by locating the atrial tissue betweentwo bipolar wire electrodes, and clamping the tissue. The forcepsconsist of two electrode pads of opposite polarity designed to grasp andclamp tissue. A well-known method of determining the status of thetissue between the electrode pads is to monitor the current, voltage,and impedance of the tissue, as done using the Richard Wolf generatorfor bipolar forceps. It is well known in the art that the ablativestatus of tissue clamped between two bipolar electrodes can easily bedetermined by monitoring the increase in tissue impedance as the tissuedesiccates.

This device is to be used with an RF generator that monitors current,voltage, and impedance to determine the state of tissue ablation of thetissue compressed between the inner and outer electrodes. The RFgenerator will be equipped with an indicator which informs the user ofthe status of the clamped tissue, and when ablation is complete (i.e.,transmural along the entire length of the electrodes).

This device provides the capability of creating long, transmural lesionsthrough atrial wall tissue of varying thickness because it employs anactive bipolar electrode on each side of the atrial wall, and theablation proceeds from both the inside and outside of the atrial wall.The device is also unique in that the electrodes are used to compressthe tissue to be ablated. This compression is critical because theinside and outside surfaces of the atrium can have irregularities, and ahigh clamping pressure insures that both electrodes are making goodcontact with tissue along the full length of each electrode. Clampingthe tissue also reduces the distance between the electrodes, and makesthe ablation more efficient because the electrical energy is moreconcentrated. Because of this higher concentration of energy, lowerpowers and temperatures can be used to achieve complete ablation, andthe process is considerably faster.

As an example, to fully ablate a 5 mm deep lesion, 30 cm long can takeseveral minutes with an endocardial catheter electrode array, and thetemperatures can be as high as 80 to 90 degrees centigrade at the tissuesurface with the generator power as high as 40 to 50 watts. In benchtoptesting of the present invention in animal hearts, a fully transmural 30mm line through 5 mm of tissue was achieved in 5 seconds at 20 watts.

With reference to FIGS. 53-54, a further embodiment of the device isshown. The device consists of an inner wire electrode wire electrode201, an outer wire electrode 202, an inner slider button 203, an outerslider button 204, and a clamping slider tube 205 and button 206. Thedevice body 207 houses the wire electrodes, slider tube and buttons,connector wires 207 a and 208, and bipolar connector 209. The device mayalso include slit needle introducer tip 210.

The operation of the device begins by advancing the inner electrode wire201 by advancing the slider button 203. Once the inner electrode 201 isadvanced to the desired length, the outer electrode 202 is advanced byadvancing slider button 204. Note that further advancement of sliderbutton 204 also advances slider button 203, so that both electrodes 201and 202 advance simultaneously. Because of the bend 202 a in theelectrode wire 202, and the notch 205 a in the slider tube assembly 205,the slider tube advances along with the outer electrode 202. Once bothelectrodes are advanced to the desired length, the slider tube 205 isadvanced so that the end 205 b of the slider tube 205 contacts thearcuate wire segment 202 b of electrode wire 202. Further advancement ofslider tube 205 acts to compress the electrode wires 201 and 202together along the entire effective length L.

FIGS. 55 and 56 show two types of electrode wires, a piercing tip (FIG.56), and an obturator, or blunt tip (FIG. 55). The electrodes may besimilar in construction to those shown in FIGS. 2-6, which are describedabove. FIG. 57 shows a side view of the instrument tip.

FIG. 58A shows the instrument used to penetrate the wall of a holloworgan, such as the heart. The slit needle 210 penetrates tissue throughthe wall of the atrium 218. In FIG. 58B, the inner wire electrode 201 isadvanced through the puncture wound into the interior of the atrium. InFIG. 58C, the outer needle 202 is initially advanced onto the externalsurface of the atrial wall 218. FIG. 58D shows the inner 201 and outer202 needles as they are simultaneously advanced along the inner andouter surfaces of the atrial wall 218. FIG. 58E shows the pusher tube205 advanced to compress the tissue of the atrial wall 218 at location219. RF energy is then applied between the conductive strips 212 on eachelectrode to ablate the compressed tissue 219. FIG. 58F shows sectionB-B of FIG. 58E, with the inner 201 and outer 202 electrodes compressingthe tissue 219. The area of ablated tissue is shown as 220. Thealternate electrode configuration of FIG. 5 is shown in FIG. 58G. Bloodcells are represented as 221.

The compression of the tissue is important because it insures that theexposed electrode surface is not in contact with any tissue or bloodexcept the clamped tissue to be ablated. Referring to FIGS. 58F and 58Gone can see that the clamping of the tissue between the electrodesinsures that only the conductive area is in contact with the clampedtissue. Especially important is avoiding any contact between theconductive area of the electrode and blood in the atrium. Contactbetween an active electrode and blood in the atrium is major cause ofthrombus formation in ablation procedures. The compressed tissue acts toisolate the electrically active surface, and prevents inadvertent energydelivery to other parts of the heart or blood. The outside temperatureof the electrode can easily be monitored to insure that the temperatureof the insulation in contact with blood remains below a criticaltemperature (40° C., for example).

FIG. 59 shows a potential series of continuous transmural ablation lines222 located around the pulmonary veins 223 in the left atrium 224. Aseries of puncture wounds 225 are shown as one means to achieve thepattern of ablation lines (shown in dot-dash lines).

FIG. 60A shows a method for achieving a circumferential lesion in apulmonary vein 223. The inner needle 201 is a piercing tip as shown inFIG. 56. The needle is advanced completely through the wall of thepulmonary vein until it exits the vein. In FIG. 60B, the outer electrode2 is advanced parallel to the inner electrode 201. In FIG. 60C, theelectrodes are compressed, and the compressed vein wall tissue 226 isablated by applying RF energy between the two electrodes. In FIG. 60D,the electrodes are released, and the vein wall tissue 226 returns to itsoriginal shape. FIG. 60E shows the outer electrode 202 retracted backinto the instrument body, and the instrument is rotated 180 degreesabout the axis of electrode 201.

FIG. 60F shows the outer electrode 202 advanced along the opposite sideof the pulmonary vein from the ablated tissue 220. In FIG. 60G, theelectrodes are compressed, and the compressed vein wall tissue 227 isablated by applying RF energy between the electrodes. FIG. 60H shows theposition of the electrodes with the pusher tube retracted, and the fullycircumferential lesion 220. FIG. 60I shows the instrument retracted fromthe vein, and the circumferential lesion of ablated tissue 220.

FIGS. 61A-61J show the instrument used in a method to create acircumferential lesion around a pair of pulmonary veins 226 and 227. InFIG. 61A the inner electrode 201 is advanced into the side of the atrialwall 218, just below the ostium of the pulmonary vein 226 by advancingslider button 203. FIG. 61B shows electrode 201 and slider 203 fullyadvanced, and exiting the atrial tissue 218 just below the ostium ofpulmonary vein 227. FIG. 61C shows outer electrode 202 advanced fully inparallel and to the same length as inner electrode 201 by advancingslider 204. Note that slider tube button 205 has advanced to itsintermediate position.

FIG. 61D shows slider button 205 fully advanced, which clamps electrodes201 and 202 together just below the ostia of the pulmonary veins on theside of the veins indicated by tissue surface 218 a, and compresses theatrial wall tissue. RF energy is then applied between the twoelectrodes, and the clamped tissue 219 is ablated. In FIG. 61E,electrode 202 is retracted by retracting slider button 4. The line ofablated tissue is shown as 219 a. This line of ablated tissue 219 a willbe completely continuous and transmural, and connect inner needle entrypoint 229 with inner needle exit point 230 and extend along the side ofthe atrial wall.

FIG. 61F shows the device body 207 rotated 180 degrees about the axis ofthe inner electrode 201 so that the atrial surface 218 b on the oppositeside of the pulmonary veins is exposed. FIG. 61G shows slider button 204and outer electrode 202 advanced over the opposite surface of the atrium218 b. FIG. 61H shows slider button 205 advanced, and the electrodes 201and 202 clamping the tissue 219 b just below the ostia of the pulmonaryveins 226 and 227 along atrial wall 218 b. RF energy is then appliedbetween the electrodes 201 and 202 to ablate the compressed tissue 219b. In FIG. 61I the slider button 205 is retracted, and the electrodesrelease the tissue 219 b. The outer electrode is then retracted,exposing the tissue 219 b that is now fully ablated as indicated by theline 219 b. FIG. 16J shows a top view of FIG. 61I showing the continuousline of ablated tissue surrounding pulmonary veins 226 and 227,connected by entry point 229 and exit point 230 of internal electrode201. The electrode is then retracted, leaving a continuous transmurallesion that electrically isolates the pulmonary veins form the rest ofthe atrial tissue.

In another embodiment of the invention, a penetratingcompressive/tensile electrode is used. Once the jaws are positionedbelow the ostia of the pulmonary veins, the tissue is partially clamped,allowing continued flow from the pulmonary veins to the left atrium. Anelectrode needle is introduced which enters the left side of the atrialtissue and exits on the right side into a tip securing point on thelower jaw. This point will prevent the tip from moving axially when aneedle is pushed. The lower atrial tissue can be compressed by “pushing”on the needle with a force that compresses tissue between the needleelectrode and the lower jaw electrode. Bipolar RF energy is then appliedbetween the needle and lower jaw electrodes to ablate a line of tissuefrom the needle entry to exit point.

Once the lower atrial tissue has been ablated, the upper jaw is moveddown to contact the tip of the lower jaw. Note that this still providesan open lumen for blood flow from the pulmonary veins to the leftatrium. The needle is rotated 180 degrees on its axis so that theelectrode surface faces up. The needle is then “pulled” to createtension, and exert a compressive force that compresses tissue betweenthe needle electrode and the upper jaw. Bipolar RF energy is thenapplied between the needle electrode and upper jaw to ablate the tissue.Note that the partial closing of the upper jaw to contact the tip of thelower jaw could be done prior to compressing the lower atrial tissue.

With reference to FIGS. 62A-62I the clamping apparatus as generallydescribed above is shown. As illustrated, the device is a “pliers type”apparatus. The device is shown clamped around the atrial tissue belowthe ostia of the pulmonary veins. In FIGS. 62B-62D, an electrode needleis advanced through the atrial tissue to contact a receiver at the tipof the device. FIG. 62E shows one method of clamping the tissue to arigid needle electrode, using a non-rigid outer clamping member thatflexes either by further motion of the handle as shown or by furtherextension of the electrode member. FIG. 62F shows both sides of theclamping member flexed, and the tissue compressed between. FIG. 62Gshows the position of the clamping members and electrode prior to tissueclamping. FIG. 62H shows these positions during tissue clamping. BipolarRF energy is applied between the clamping members, and the innerelectrode to ablate the atrial tissue, creating a lesion, as shown inFIG. 62H. Note also, that if the inner electrode had only one exposedelectrode surface, the tissue ablation could be carried out first on oneside, then the other, without occluding the lumen between the pulmonaryveins and the atrium.

FIG. 62I shows another way to achieve tissue compression by advancing arelatively flexible needle electrode which bends as shown to compressthe tissue between the electrode and one of the device jaws.

Thus, it can be seen that a transmural ablation device and method havebeen provided that overcome the limitations of the prior art. First,current technology involves ablation devices deliver ablation energy toeither the inside (endocardium) or outside (epicardium) of the heart.Using these techniques, the tissue ablation proceeds from one wall ofthe heart through the tissue to the opposite wall. To date, there hasbeen no reliable way to consistently achieve lesions that penetrate thefull thickness of the atrial wall (transmural lesions), and there hasbeen no way to determine either continuity or transmurality of theselesions. If the lesion does not penetrate through enough of the atrialwall, conduction can still occur, and the lesion does not fully blockthe electrical signals that are causing the arrhythmia. Using anendocardial approach, if the lesion penetrates too far through the wall,critical structures such as coronary arteries, veins, or the esophaguscan be damaged on the outside of the heart. Using an epicardialapproach, if the lesion penetrates too far, blood can be coagulated, orcritical structures such as valves, nodes, or connective tissue can bedamaged on the inside of the heart.

There has also been no reliable and consistent way to safely achievefully continuous, long (greater than 1 cm) lesions in the atrial wallwithout a high risk of thrombus, damage to critical structures, orextensive damage to the atrial tissue.

The present invention overcomes these shortcomings because theconductive area of each electrode is very narrow compared to the widthof the clamped area. As a result, the thermal damage to the tissue isminimal. In contrast, current technology uses catheter electrodes whichare typically 1 or 2 mm diameter requiring a lesion width of almost 8 mmto achieve a depth of 5 mm. Using the present invention, a lesion depthof 5 mm with a width of less than 2 mm can be achieved. This aspect ofthe invention allows for longer linear lesions with less power deliverybecause less tissue is being heated. There is, therefore, considerablyless damage to healthy atrial tissue for a lesion of a given depth andlength. Recent efforts in creating linear lesions using endocardialelectrodes resulted in ablation of over 20% of the atrial endocardium,and a commensurate decrease in atrial contractility.

Another advantage of this device is that ablation can be done on abeating heart. Using a high modulus material such as tungsten or carbonfiber would allow a minimum diameter, and a maximum clamping pressurefor a given clamping length. Once the device is clamped onto the atrialwall, the position of the electrodes can be verified by visuallyinspecting the position of the outer electrode before delivery of RFenergy. If the clamping pressure is higher than the atrial pressure,then clamping over a coronary artery would cut off blood flow, and theresulting change in the EKG would act as a warning to the user prior toapplying RF energy. The clamping will prevent any movement of theelectrodes relative to the heart wall, and RF energy can be applied withconfidence that the ablated tissue will be contained completely betweenthe two electrodes.

Another important feature of this device is that the energy transfer islimited to the tissue clamped between the two electrodes. The insulatedelectrodes protect structures on the outside of the heart from beingexposed to RF energy. Because of this limitation of current flow, damageto critical structures can be avoided.

Another advantage of this device is that it can easily be adapted to aminimally invasive thoracoscopic approach. The device shown has beenreduced to a 5 mm diameter device, and can probably be reduced to 3 mmor less. Using video thoracoscopy, the device could be introducedthrough a small intracostal incision, and used to create fullytransmural linear lesions on a beating heart, possibly under localanesthesia on an anesthetized patient.

Accordingly, a device for performing transmural ablation has beenprovided that meets all the objects of the present invention. While theinvention has been described in terms of certain preferred embodiments,there is no intent to limit the invention to the same. Instead it is tobe defined by the scope of the appended claims.

1. An electrosurgical clamp for forming transmural lesions in cardiactissue, the clamp comprising: first and second jaws relatively pivotablymovable about a respective pivot between an open position for receivingcardiac tissue therebetween and a clamped position to compress thetissue therebetween; one of the jaws being independently relativelyshiftable at the respective pivot relative to the other jaw to allowspacing between the jaws at the respective pivot to increase in theclamped position with the presence of tissue between the jaws; and afirst electrically conductive element carried by the first jaw and asecond electrically conductive element carried by the second jaw, theelectrically conductive elements being adapted to be connected to an RFenergy source so that the first and second electrically conductiveelements direct electrical current through the cardiac tissue compressedtherebetween to form a transmural lesion through the tissue.
 2. Theclamp of claim 1 in which, the first jaw includes a pivot pin and thesecond jaw includes a pivot slot receiving the pivot pin, the pivot pinbeing pivotable within the slot for relative pivoting of the jaws andbeing movable along the slot for relative shifting of the jaws.
 3. Theclamp of claim 2 comprising a spring biasing the pivot pin to a selectedlocation in the pivot slot.
 4. The clamp of claim 1 in which the jawsare biased to a selected shifted position.
 5. The clamp of claim 1wherein the jaws are relatively shiftable in the vicinity of therespective pivot to allow the jaws to reach a substantially parallelclamped position over a range of spacing between the jaws correspondingto cardiac tissue of differing thickness.
 6. The clamp of claim 1wherein the clamp comprises a linearly movable rigid member, and meansconnecting the member and the jaws for moving the jaws between receivingand compressing positions upon linear movement of the member.